The Astros selected Scott's contract from Triple-A Sugar Land on Thursday, Brian McTaggart of MLB.com reports.
Scott signed a minor-league contract with the Astros on Dec. 12.
The Athletics outrighted Scott to Triple-A Las Vegas on Monday.
The Athletics optioned Scott to Triple-A Las Vegas on Tuesday.
Scott was recalled from Triple-A Las Vegas on Tuesday, Martin Gallegos of MLB.com reports.
Scott was optioned to Triple-A Las Vegas on Saturday.
Scott will start Tuesday's game against the Giants as Oakland's opener.
Scott was claimed off waivers by the Athletics on Wednesday.
Scott was designated for assignment by the Red Sox on Sunday, Christopher Smith of The Springfield Republican reports.
Scott will serve as the opener for Sunday's game against the Athletics, Chris Cotillo of The Springfield Republican reports.